Machining method and machining device improving machining efficiency and preserving workpiece surface integrity

ABSTRACT

Disclosed are a machining method and a machining device improving machining efficiency and preserving workpiece surface integrity. The machining method improving machining efficiency and preserving workpiece surface integrity includes: setting a workpiece ( 300 ) and a machining unit ( 400 ); and machining the workpiece ( 300 ) by the machining unit ( 400 ) at a preset machining speed, wherein the preset machining speed is not lower than a machining speed corresponding to the embrittlement of the workpiece material. By the machining method, the machining speed of the machining unit ( 400 ) is set during machining, which results in “skin effect” of subsurface damage caused by the embrittlement of the workpiece material ( 300 ) and enables the damage depth of the workpiece ( 300 ) to be confined in a shallow subsurface layer, so that the damage depth of the workpiece ( 300 ) is reduced, the workpiece integrity is preserved, and the machining quality and the machining efficiency are improved.

TECHNICAL FIELD

The present disclosure relates to the technical field of materialmachining, and in particular, to a machining method and a machiningdevice improving machining efficiency and preserving workpiece surfaceintegrity.

BACKGROUND

Materials, such as ductile materials, hard and brittle materials, andcomposite materials, have good mechanical and physical properties, andare widely used in the fields of aerospace, defense, semiconductors,automobiles, cutting tools, and the like. The abovementioned materialsare difficult to machine, and have the defects of low machiningefficiency, low precision, and poor surface quality during machining.

SUMMARY

The present disclosure aims to solve at least, one of the technicalproblems in the prior art. In view of this, the present disclosureprovides a machining method that can have a high efficiency andsimultaneously preserve surface integrity of a workpiece duringmachining.

The present disclosure further provides a machining device for executingthe machining method that can have a high efficiency and simultaneouslypreserve surface integrity of a workpiece.

In a first aspect, one embodiment of the present disclosure provides amachining method improving machining efficiency and preserving workpiecesurface integrity, which includes:

setting a workpiece and a machining unit; and

machining the workpiece by the machining unit at a preset machiningspeed, where the preset machining speed is not lower than, the machiningspeed corresponding to the embrittlement of the workpiece.

The machining method improving machining efficiency and preservingworkpiece surface integrity in the embodiment of the present disclosureat, least has the following beneficial effects.

In the embodiment of the present disclosure, the workpiece is machinedby the machining unit at the preset machining speed, which results inthe embrittlement of the workpiece material, causes the “skin effect” ofsubsurface damage, and enables the damage depth of the workpiece to bein a shallow subsurface layer. As a result, the damage depth of theworkpiece is reduced, the workpiece surface integrity is preserved, andthe machining quality and the machining efficiency are improved.

According to the machining method improving machining efficiency andpreserving workpiece surface integrity of some other embodiments of thepresent disclosure, the preset machining speed is that corresponding tothe embrittlement of a material or the ductile matrix component in acomposite material, or is not less than 150 m/s.

According to the machining method improving machining efficiency andpreserving workpiece surface integrity of some other embodiments of thepresent disclosure, the workpiece is machined in one or more forms ofgrinding, turning, and milling.

According to the machining method improving machining efficiency andworkpiece surface integrity of some other embodiments of the presentdisclosure, the workpiece is machined repeatedly for a plurality oftimes, and the machining depth of the machining unit is different eachtime.

According to the machining method improving machining efficiency andworkpiece surface integrity of some other embodiments of the presentdisclosure, the workpiece is machined repeatedly for a plurality oftimes, and the machining depth of the machining unit is graduallyreduced time by time.

According to the machining method improving machining efficiency andworkpiece surface integrity of some other embodiments of the presentdisclosure, the workpiece is machined repeatedly for a plurality oftimes, and the particle size of the machining unit is gradually reducedstep by step.

According to the machining method improving machining efficiency andworkpiece surface integrity of some other embodiments of the presentdisclosure, ultrasonic vibration is performed while machining theworkpiece.

In a second aspect, one embodiment of the present disclosure provides amachining device improving machining efficiency and preserving workpiecesurface integrity, which is used for executing the machining methodhaving the same merits. The machining device includes:

a base, used for mounting the workpiece and the machining unit; and

a driving unit, connected to the machining unit and used for driving themachining unit to the preset machining speed.

The machining device improving machining efficiency and preservingworkpiece surface integrity in the embodiment of the present disclosureat least has the following beneficial effects.

In the embodiment of the present disclosure, the machining speed of themachining unit is increased through power driving of the driving unit tothe machining unit, so that the damage depth of the workpiece isconfined in a shallow subsurface layer, and the damage depth of amachined workpiece subsurface is reduced, thereby improving themachining quality of the workpiece.

According to the machining device improving machining efficiency andworkpiece surface integrity of some other embodiments of the presentdisclosure, the machining device further includes an ultrasonic unit.The ultrasonic unit is connected to the machining unit, so that themachining unit, performs ultrasonic vibration.

According to the machining device improving machining efficiency andpreserving workpiece surface integrity of some other embodiments of thepresent disclosure, the machining device further includes a detectionelement used for detecting the machining speed of the machining unit.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic flowchart of a material machining method in theembodiments of the present disclosure;

FIG. 2 illustrates fitting curves of material strain-rates and materialbrittleness changes;

FIG. 3 illustrates fitting curves of material strain-rates and materialdamage depths; and

FIG. 4 is a structural schematic diagram of a material machining devicein the embodiments of the present disclosure.

DETAILED DESCRIPTION OF THE EMBODIMENTS

The conception and the achieved technical effects of the presentdisclosure will be described below clearly and completely in combinationwith the embodiments, so as to fully understand the purposes, thefeatures, and the effects of the present disclosure. Apparently, thedescribed embodiments are merely part rather than all of the embodimentsof the present disclosure. Based on the embodiments of the presentdisclosure, all other embodiments obtained by those skilled in the artwithout creative work belong to the scope of protection of the presentdisclosure.

In the description of the present disclosure, if orientation descriptionis involved, for example, orientations or positional relationshipsindicated by “upper”, “lower”, “front”, “rear”, “left”, “right”, etc.are orientations or positional relationships shown based on theaccompanying drawings, they are merely used for the convenience ofdescribing the present disclosure and simplifying the description,rather than indicating or implying that the devices or elements must,have particular orientations, and constructed and operated in particularorientations. Thus, it cannot be construed as a limitation to thepresent disclosure.

In the description of the embodiments of the present disclosure, if acertain feature is called “arranged”, “fixed”, “connected”, or “mounted”on another feature, it can be directly arranged, fixed, or connected toanother feature, or can also be indirectly arranged, fixed, connected,or mounted on another feature. In the description of the presentdisclosure, if “a plurality of is involved, it means more than one; ifmultiple” is involved, it means more than two; if “greater than”, “lessthan”, and “more than” are involved, it should be construed as excludingthe number; and if “above”, “below” and “within” are involved, it shouldbe construed as including the number. If “first” and “second” areinvolved, it should be construed as distinguishing technical features,but cannot be construed as indicating or implying relative importance orimplicitly indicating the number of indicated technical features orimplicitly indicating the precedence relationship of the indicatedtechnical features.

Referring to FIG. 1 , the embodiments of the present disclosure providea machining method improving machining efficiency and preservingworkpiece surface integrity, which includes the following machiningsteps:

first, a workpiece to be machined and a machining unit used formachining the workpiece are set; and

then, the workpiece is machined by the machining unit at a presetmachining speed, where the preset machining speed is not lower than themachining speed-corresponding to the material embrittlement of theworkpiece.

It should be noted that, during high-speed machining of a material,internal defects of the material are activated under an impact load,which results in the nucleation, propagation, and intersection ofmicro-cracks, and produces more cracks in a surface layer of thematerial, thereby resulting in the embrittlement of the material. Thematerial resistance at the tip of a produced crack of the material willincrease with the increase of a strain-rate, which hinders thepropagation of the crack and reduces the damage depth, thereby resultingin the “skin effect” of subsurface damage caused by the embrittlement ofthe material. FIG. 2 lists fitting curves between the damage depths ofseveral materials and the brittleness change of the materials. Thehorizontal coordinate axis is the brittleness change of the materials,and the longitudinal coordinate axis is the damage depths of thematerials. It can be seen that the material brittleness increases alongwith the increase of the machining speed or the strain-rate, and thesubsurface damage introduced by machining is only distributed in ashallow subsurface layer of the workpiece, so as to reduce the damagedepth of the material during machining and improve the machiningefficiency.

In addition, by fitting relation curves between the subsurface damagedepths and the strain-rates of the materials, referring to FIG. 3 , thehorizontal coordinate axis represents the strain-rate of the material,and the longitudinal coordinate axis represents the subsurface damagedepth of the material. In mathematical expression, the relationshipbetween the subsurface damage depth and strain-rate of the material is:

$\begin{matrix}{\delta = {k_{1} \cdot ( \frac{d\varepsilon}{dt} )^{- 0.34}}} & (1)\end{matrix}$

The relationship between the, machining speed of the material and thestrain-rate of the material is:

$\begin{matrix}{\frac{d\varepsilon}{dt} = {k_{2} \cdot v}} & (2)\end{matrix}$

where, δ represents the damage depth, k₁ and k₂ are dimensionlessparameters, dε/dt is the strain-rate of the workpiece material, and v isthe machining speed of the workpiece.

It can be seen from Formula (2) that the strain-rate of the material isin direct proportion to the machining speed, and the strain-rate of the,workpiece material is increased due to the increase of the speed of themachining unit. k₂ is related to the size of the material and themachining depth, and can be calculated by deriving a formula.

It can be seen from Formula (1) that the subsurface damage depth of thematerial is in direct proportion to a negative exponent of thestrain-rate, that is, the subsurface damage depth of the workpiecedecreases with the increase of the machining speed and gradually trendsto the surface layer, so that the “skin effect” of subsurface damage ofthe workpiece is achieved. By increasing the machining speed, thesubsurface damage of the workpiece can be reduced, the machiningefficiency of the workpiece can be improved, and the machining qualitycan be ensured.

The damage “skin effect” is an inherent characteristic of an engineeringmaterial, that is, in a high strain-rate loading process of a workpiece,the damages (such as crack, dislocation, and phase change) and the likeof the material are concentrated in a local loading regime withoutextensive propagation, so that the subsurface damage depth decreaseswith the increase of the machining speed or the strain-rate. In thepresent disclosure, the workpiece is machined at the preset machiningspeed, so as to reduce the subsurface damage depth. The preset machiningspeed is the machining speed corresponding to the embrittlement of theworkpiece material. For a ductile material, the preset machining speedrefers to the machining speed corresponding to the embrittlementthereof. For a hard and brittle material, the preset machining speedrefers to the conventional high speed machining speed (the machiningspeed is over 150 m/s). For a composite material, the preset machiningspeed refers to the machining speed corresponding to the embrittlementof the ductile matrix component in the material.

The “skin effect” of the material damage exists in the machining of thehard and brittle material, the ductile material, the composite material,and the like. It should be noted that the present disclosure aims at theworkpiece materials, including the hard and brittle material, theductile material, the composite material, and the like. During themachining of hard and brittle materials, with the increase of themachining speed, the brittleness increases, the machining chips becomesmaller, the subsurface damage depth decreases. For the ductilematerial, the plastic deformation of the material is inhibited, bymachining at a high speed, the material is removed in a brittle fractureform, the temperature of a machining regime is suppressed, and thethickness of a metamorphic layer in the workpiece subsurface is reduced.During machining at a high speed, the material is in a high-strain-ratestate. The embrittlement of the ductile material or the brittleness ofthe hard and brittle material can be improved due to the strain-ratehardening effect during the machining, so that the subsurface damagedepth is reduced by the “skin effect” of the workpiece subsurfacedamage.

The machining speed corresponding to the embrittlement of a ductilematerial or the ductile matrix component in a composite material may bejudged by observing the shapes of machining chips, the morphology of thechips, the workpiece surface hardening degree, the workpiece surfacequality, and the like at different machining speeds (machiningstrain-rates), so as to identify that the material is in a plasticfracture state or a brittle fracture state. For example, during themachining of the ductile material, with the increase of the machiningspeed, the machining chips change from continuous to discontinuous,reflecting the characteristics of brittle fracture. At this moment, theworkpiece material within the machining zone is embrittled, so that themachining state of the workpiece is characterized by the shapes of thechips.

In a general low-speed machining situation, the chip of a ductilematerial is typically continuous, while the chip of a brittle materialis in a fragmented shape. With gradual increase of the machining speed,the ductile material will be embrittled, and the chips thereof arechanged from continuous bands into a serrated or a fragmented shape.Taking 7050-T7451 aluminum alloy as an example, the aluminum alloy is atypical ductile material. When the aluminum alloy is machined at thecutting speed of 1,257 m/min, the chips are in an obvious serratedshape. At this moment, the aluminum alloy is embrittled.

The embrittlement of the workpiece material is related to the factors,such as the machining temperature of the workpiece, the machining loadapplied by the machining unit, the machining depth, the machining speed,the workpiece material, and the like. The machining speed correspondingto the embrittlement of the workpiece material may be experimentallyobtained by fixing other parameters and adjusting the machining speed ofthe machining unit.

The machining unit and/or the workpiece may also be positioned beforethe workpiece is machined, so that the machining unit performs machiningat a preset machining depth and a corresponding machining position ofthe workpiece, so as to ensure the machining accuracy. The machiningmode of the abovementioned machining unit on the workpiece may beselected according to a specific machining process of the workpiece,such as grinding, turning, and milling. The type of the machining unitmay also be selected according to a specific machining process of theworkpiece, such as a grinding wheel, a turning tool, a milling tool. Themachining speed of the machining unit may refer to the moving speed andthe feeding speed of the machining unit relative to the workpiece, therotating speed of the machining unit, and the like.

The machining mode of the workpiece by the machining unit may adopt amode that the machining unit moves or rotates or moves and rotatesrelative to the workpiece. For example, the machining unit is set as themilling tool, the milling tool moves relative to the workpiece accordingto a predetermined trajectory, so as to realize the milling of theworkpiece; or the machining unit is set as the turning tool, the turningtool feeds gradually relative to the workpiece, so as to realize theturning of the workpiece; or the machining unit is set as the grindingwheel which applies a continuous grinding force to the workpiece whilerotating and moving relative to the workpiece, so as to realize thematerial removal of the workpiece. The application range of themachining method provided by the embodiments of the present disclosureis wide, and a corresponding machining mode may be selected to machinethe workpiece according to different machining requirements.

The machining depth of the workpiece has an upper limit. When themachining depth of the workpiece is great, if a preset machining depthis reached by only performing single machining, the damage degree of theworkpiece is serious, and the machined workpiece is also easily damaged.In order to meet the process requirements of the machining depth and themachining quality at the same time, the workpiece needs to be machinedcircularly for a plurality of times and gradually feeds to a presetthickness.

Specifically, a single machining depth is set to machine the workpiecetime by time until the preset machining depth is reached according tothe machining depth requirement of the workpiece. The single machiningrefers to that the machining unit completes the machining of the wholesurface to be machined of the workpiece on the premise of the presetmachining depth of this time. According to the characters of thematerial and specific machining requirements, different machining depthsmay be set for the machining unit each time, so that the machining depthadapts to the machining situation of the workpiece of this time, and theworkpiece machining flexibility is improved. Following the principle ofrough machining before finish machining, a great machining depth may beset first, and the machining depth may be reduced step by step with theincrease of machining times, so as to reduce the workpiece damage depthand improve the quality of the workpiece surface on the premise ofensuring that the workpiece has sufficient machining depth. In addition,different machining depths may be executed by selecting differentmachining workpieces, for example, the workpiece is ground after beingcut by a certain thickness by using a cutting tool, which takes both themachining efficiency and the machining quality into consideration.

In actual production, machining units with different particle sizes andhardness may be selected to machine the workpiece according to thespecific machining requirements of the workpiece. The particle sizerefers to the size of the particles in the machining unit for performingmain machining on the workpiece. The smaller the particle size of themachining unit, the smaller the damage depth of the workpiece. Themachining unit with a larger particle size can realize the roughmachining of the workpiece, and can quickly eliminate the defects on theworkpiece surface or the damage caused in the previous process, so thatthe workpiece surface has certain flatness. The machining unit with asmaller particle size can realize the finish machining of the workpiece,ensure the integrity and the flatness of the workpiece surface, reducesubsequent machining processes, and shortens the machining time. In thepresent embodiment, the workpiece is machined repeatedly for a pluralityof times, and the particle size of the machining unit is reduced step bystep, so as to ensure the machining, efficiency of the workpiece and thesurface quality of the workpiece.

In order to further optimize the machining quality of the workpiece, themachining unit with the smaller particle size can be selected, so as toimprove the machining speed of the machining unit. The machining speeddoes not exceed the machining speed corresponding, to the embrittlementof the workpiece material, and a single machining depth is reduced, soas to realize high-efficiency and low-damage machining and improve thesurface quality of the workpiece.

In another embodiment, during the machining of workpieces, an ultrasonicvibration unit is added, which can reduce the grinding force, improvethe stability of a machining system, reduce a friction force between acutting tool and the workpiece, reduce the generation of grinding heat,reduce or avoid a problem of burning of the workpiece surface, can alsoreduce the roughness of the workpiece surface, and improve the machiningquality of the workpiece surface.

Referring to FIG. 4 , the embodiments of the present disclosure furtherprovide a machining device improving machining efficiency and preservingworkpiece surface integrity. The machining device is used for executingthe abovementioned material machining method. The material machiningdevice includes a base 100 and a driving unit 200. The base 100 is usedfor mounting a workpiece 300 and a machining unit 400. The base 100provides an operation platform for the movement of the machining unit400 and the machining of the workpiece 300. The driving unit 200 isconnected to the machining unit 400 and provides power support for themachining unit 400, so that the machining unit 400 machines theworkpiece 300 at a preset machining speed.

The machining speed of the machining unit 400 is increased through powerdriving of the driving unit 200 to the machining unit 400, so that thedamage depth of the workpiece 300 is confined in a surface layer, andhigh-efficiency and low-damage machining is realized. By limiting themachining speed of the machining unit 400, the workpiece 300 isprevented from brittle fracture, and the surface integrity of theworkpiece 300 is affected.

The machining unit 400 may move and/or rotate relative to the workpiece300. The driving unit 200 may be one or a combination of more of anelectric machine, a motor, a cylinder, and the like, so as to realizethe movement and/or rotation of the machining unit 400 relative to theworkpiece 300. The type of the machining unit 400 may be selectedaccording to actual use requirements, such as a grinding wheel, aturning tool, and a milling tool.

A fixture for clamping or fixing the workpiece 300 may be arranged onthe base 100, so that the workpiece 300 is kept in a static state duringmachining, thereby improving the machining precision. The fixture may bea platform for providing a placement plane for the workpiece 300, or afixture capable of adsorbing the workpiece 300, or a manipulator capableof clamping the workpiece 300, or the like. A plurality of workpieces300 may be arranged on the fixture at one time, so that the machiningunit 400 can machine the plurality of workpieces 300 at one time,thereby improving the machining efficiency of the machining device.

A first moving module 110 may also be mounted on the base 100. A clampis mounted on the first moving module 110, and is driven to move throughthe first moving module 110. so as to facilitate the positioning betweenthe machining unit 400 and the workpiece 300. Thus, the machining unit400 may machine different areas of the workpiece 300. The first movingmodule 110 may be provided with not less than two groups of movingcomponents. The extension directions of moving guide rails in differentmoving components are different, so that the position of the workpiece300 can be adjusted in different directions.

A second moving module 120 may also be arranged on the base 100. Thesecond moving module 120 may drive the machining unit 400 to move in thevertical direction, so that the machining unit 400 feeds close to theworkpiece 300, or moves away from the workpiece 300 to avoid for themovement of the workpiece 300. The machining depth of the workpiece 300by the machining unit 400 can be adjusted by moving the machining unit400 in the vertical direction, so that the machining device adapts todifferent machining requirements. The second moving module 120 may alsoinclude a plurality of groups of moving components. The machining unit400 is mounted on the moving components, and the position of themachining unit may be adjusted in a horizontal, plane under the drivingof the moving components, so as to realize the movement of the machiningunit 400 relative to the workpiece 300, thereby enabling the machiningunit 400 to machine different areas of the workpiece 300.

On the premise of meeting the moving requirement of the machining unit400 and the workpiece 300, the abovementioned first moving module 110and second moving module 120 may select the existing automatic ormanual, moving modules.

In another embodiment, an ultrasonic unit 130 is also arranged on thedriving unit 200. The machining unit 400 forms ultrasonic vibrationunder the influence of the ultrasonic unit 130. The ultrasonic vibrationassists in machining the workpiece 300 by the machining unit 400, whichcan effectively reduce or avoid the problem of surface burning of theworkpiece 300, and improve the surface machining quality of theworkpiece 300.

A detection element for detecting machining parameters of the machiningunit 400 may also be arranged on the base 100, for example, adisplacement sensor is arranged for detecting the machining depth of themachining unit 400, a pressure sensor is arranged for testing an actingforce of the machining unit 400 applied to the workpiece 300, and aspeed sensor is arranged for detecting the machining speed of themachining unit 400, so as to facilitate the acquisition of real-timemachining parameters of the machining unit 400, thereby ensuring themachining precision of the workpiece 300.

The abovementioned machining device improving machining efficiency andpreserving workpiece surface integrity may be applied to machiningequipment, such as a turning machine, a milling machine, and a grindingmachine, so as to enable the workpiece 300 to adapt to differentmachining requirements, and improve the machining quality of theworkpiece 300 in different machining environments.

The embodiments of the present disclosure are described in detail incombination with the accompanying drawings above, but the presentdisclosure is not limited to the abovementioned embodiments. Within thescope of knowledge possessed by those of ordinary skill in the art,various changes can be made without departing from the purpose of thepresent disclosure. h addition, the embodiments of thepresent-disclosure and the features in the embodiments may be combinedwith each other without conflict.

1. A machining method improving machining efficiency and preservingworkpiece surface integrity, comprising: setting a workpiece and amachining unit; and machining the workpiece by the machining unit at apreset machining speed, wherein the preset machining speed is not lowerthan the machining speed corresponding to the embrittlement of theworkpiece.
 2. The machining method improving machining efficiency andpreserving workpiece surface integrity according to claim 1, wherein thepreset machining speed is the machining speed corresponding to theembrittlement of a material or the ductile matrix component in acomposite material, or is not less than 150 m/s.
 3. The machining methodimproving machining efficiency and preserving workpiece surfaceintegrity according to claim 1, wherein the workpiece is machined in oneor more forms of grinding, turning, and milling.
 4. (canceled) 5.(canceled)
 6. (canceled)
 7. (canceled)
 8. A machining device improvingmachining efficiency and preserving workpiece surface integrity, usedfor executing the machining method having the same merits according toclaim 1, comprising: a base, used for mounting the workpiece and themachining unit; and a driving unit, connected to the machining unit andused for driving the machining unit to the preset machining speed. 9.(canceled)
 10. The machining device improving machining efficiency andpreserving workpiece surface integrity according to claim 8, furthercomprising a detection element used for detecting the machining speed ofthe machining unit.
 11. A machining device improving machiningefficiency and preserving workpiece surface integrity, used forexecuting, the machining method having the same merits according to anyone of claim 2, comprising: a base, used for mounting the workpiece andthe machining unit; and a driving unit, connected to the machining unitand used for driving the machining unit to the preset machining speed.12. The machining device improving machining efficiency and preservingworkpiece surface integrity according to claim 11, further comprising adetection element used for detecting the machining speed of themachining unit.
 13. A machining device improving machining efficiencyand preserving workpiece surface integrity, used for executing themachining, method having the same merits according to any one of claim3, comprising: a base, used for mounting the workpiece and the machiningunit; and a driving unit, connected to the machining unit and used fordriving the machining unit to the preset machining speed.
 14. Themachining device improving machining efficiency and preserving workpiecesurface integrity according to claim 13, further comprising a detectionelement used for detecting the machining speed of the machining unit.